First, an example of a magnetic recording and reproducing apparatus will be explained referring to FIGS. 1 and 2.
FIG. 1 shows a linear skating type mechanical deck in a magnetic recording and reproducing apparatus for DV (Digital Video) formatting, for example, and indicates a state in which a movable chassis 1 has moved from a fixed chassis 2 to a position where a cassette can be detached (unloading position). Also, FIG. 2 shows a state in which the movable chassis 1 has slid and moved to a position where magnetic tape (not shown) is loaded onto a magnetic rotary head 8.
In FIG. 1, numeral 1 denotes a U-shaped movable chassis, to which pop-up type cassette compartments not shown in the figure are attached on both sides in order for a cassette to be lifted and removed easily, for example, when the cassette is loaded/unloaded. Further, the movable chassis includes a pair of reel stands 3 and 4 for supplying and taking up tape, and is provided with a reel stand cover plate 5 that covers other mechanical portions than the reel stands 3 and 4, on which a tape-end sensor light emitting portion 6, a reel-brake release projection 7 and the like are provided.
Further, as shown in FIG. 2, the magnetic rotary head 8 and a capstan 9 are provided on the fixed chassis 2, and on a guide plate 10 around the magnetic rotary head 8, guide-receiving grooves 11 and 12 are provided. The movable chassis 1 slides and moves on the fixed chassis 2 by making sliding pins 16 and 16 provided on one side surface of the U-shaped portion slide and move in slide grooves 15 and 15 provided on one side surface of the fixed chassis 2 by means of a loading gear not shown.
Each of guide rollers 13b and 13e on supplying and taking up sides provided around the magnetic rotary head 8 moves along the slide grooves 11 and 12 respectively, and when tape loading is completed, the rollers are fixed firmly to function as tape guides so that tape runs stably with respect to the magnetic rotary head 8. Further, on the mechanical deck, for example, a tape guide 13a and a slanted guide 13c are provided on the supplying side, and a slanted guide 13d, a pinch roller 9b, a tape guide 17 and other mechanisms are provided on the taking up side as other guide mechanisms, so that when loading tape, those guide mechanisms move together with the movable chassis 1 and are fixed at a predetermined position for the stable running of the tape.
As shown in FIG. 3, when a cassette 18 is loaded, those guide portions constitute a tape path system, in which a magnetic tape 19 pulled out from a providing side reel 3a is helically wound around the magnetic rotary head 8 through the tape guide 13a, a tension regulator 14, the guide roller 13b, and the slanted guide 13c; and then the magnetic tape is taken up by a taking up side reel 4a through the slanted guide 13d, the guide roller 13e, a capstan shaft 9a, the pinch roller 9b, and finally the tape guide 17.
As understood from FIG. 3, the tape guide 17 on the taking up side directly functions as the tape guide for the taking up side reel 4a. If taking-up of magnetic tape to a reel is not stably performed, the magnetic tape is contacted with a reel flange to be creased, damaged, or deteriorated due to the fact that force may not equally be applied to the whole width of the magnetic tape and so on. Accordingly, in order to maintain a favorable condition of the magnetic tape 19, it is important to maintain the height of the tape guide 17 and verticality or predetermined slant thereof with respect to the movable chassis 1 irrelevant to the diameter of the taking up side reel 4a around which the tape is wound, so that the magnetic tape 19 is constantly wound up to be a predetermined height by the taking up side reel stand 4 without a problem.
FIG. 4 shows an example of a conventional tape guide mechanism and FIG. 5 shows the cross section thereof.
On a tape guide arm member 20 constituting the tape guide mechanism, the tape guide 17 is erected and also two shafts are vertically provided, in which a rotary fulcrum shaft of the tape guide arm member 20 is constructed for accurate rotation such that a fulcrum shaft 21 that is one of the shafts vertically provided on the tape guide arm member 20 is inserted to be engaged with a long bearing boss 24 fixed to the movable chassis 1 by caulking. The upper surface of the fulcrum shaft 21 is covered with the reel stand cover plate 5.
Further, a cam shaft 22 that is the other of the shafts vertically provided on the tape guide arm member 20 acts together with the movable chassis 1 and moves in a guide groove 23 of the fixed chassis 2 and in a rotation groove 22a. 
The posture (trace) of the tape guide 17 and the tape guide arm member 20 in the middle of tape loading or when tape loading is completed is determined by the rotation fulcrum shaft 21 of the tape guide arm member 20 and the bearing boss 24 of the fixed chassis 2.
Further, the tape guide arm member 20 is forced in the counterclockwise direction (indicated by an arrow in the drawing) by a spring means such as a spring not shown. In addition, the height can be adjusted using a screwdriver or the like for a concave portion 17a with a groove on top of the tape guide 17. Numeral 17b denotes a spring means of an auxiliary component for adjusting the height.
As heretofore described, in order for the magnetic tape 19 to travel stably, the tape guide 17 is required to be accurately fixed at a predetermined position on the movable chassis 1, and accurate assembly is needed to obtain the above required position, when the bearing boss 24 is fixed to the movable chassis 1 by caulking, for example.
Further, the tape guide 17 requires accurate height adjustment and a bearing component with high accuracy is required at, for example, the rotation fulcrum portion of the tape guide arm member 20. Specifically, difference between the outer diameter of the fulcrum shaft 21 and the inner diameter of the fulcrum bearing boss 24 shown in FIG. 5 is made small. The difference of dimensions between the fulcrum shaft 21 and the bearing boss 24 when engaged with each other is approximately 0 to several ten μm conventionally, and the length for receiving a shaft (fulcrum shaft inserting length) is obtained as long as possible to restrain an inclination, so that the tape guide arm member 20 can be made to move horizontally, preventing the tape guide 17 erected on the end thereof from falling down.
However, highly sophisticated technology is required to obtain such accurate bearing component and engagement accuracy between the outer diameter of the fulcrum shaft and the inner diameter of the bearing component, which results in the problem of high cost.
Furthermore, to obtain the shaft receiving length as long as possible, there occurs such a problem that no other component can be arranged in the space in which the bearing moves around, in other words, no flexibility is available for design in the height direction of the mechanical deck.